Who said that humans are born with a built-in predisposition to learn grammar rules?

Noam Chomsky

Explanation:

Noam Chomsky is considered the "father of modern linguistics".

He had made many contribution in the field of linguistics with his various theories and books.

It is Noam Chomsky who theorized the concept of universal grammar. According to this theory, Noam asserted that all human beings have an innate ability in their minds to acquire the language. Noam Chomsky theorized this concept of universal grammar in the 1960s.

So, the correct answer is Noam Chomsky.